Safety checks ordered after huge bolts fall off the Cheesegrater

The Cheesegrater in the City of London was cordoned off after the incident (Picture: Daniel Hambury) Daniel Hambury

An urgent programme of ultrasound tests on more than 3,000 “mega-bolts” on the City’s Cheesegrater skyscraper has been ordered after two broke off from the building.

Teams from contractor Laing O’Rourke, who constructed the 47- storey tower, and structural engineers Arup have begun testing for weaknesses in the huge 5in diameter bolts that hold it together. An initial visual inspection by engineers has already been completed.

Nigel Webb, head of development at the Cheesegrater’s joint owners, property group British Land, said the process would take “weeks not months.”

He added: “Until we know what the cause is, this is the cautious thing for us to do. In layman terms, they do an ultrasound test to test the density of the bolts.”

Laboratory checks are also being carried out on the bolts that failed. British Land revealed in a Stock Exchange announcement yesterday that part of one bolt and a nut fell to the ground from the fifth floor and a second bolt broke and fell on the access gantry on the 19th floor.

British Land has put fencing around the ground floor “as a precaution only” while the tests are carried out but said there would be no need to cover the building in scaffolding. “The building is still open, it is not an unsafe structure,” Mr Webb added.

There are no mega-bolts on the northern face of the Lord Rogers-designed building.

The spotlight also turned today on Severfield, the company that installed the steel structure of the 224-metre Cheesegrater, officially known as the Leadenhall Building .

Severfield faced a £10 million cost overrun on the skyscraper and other contracts, forcing it to issue a profit warning.

A spokesman said Severfield was “working closely with all parties involved” but added: “Until we are fully aware of all the facts, it would not be appropriate to comment or speculate further.”

Meanwhile City workers today spoke of their shock at the potential consequences of the incident.

Although the bolt that hit the ground landed in an area currently cordoned off for construction, the spot will become a public space including gardens and benches when building work is completed. Private equity investment director Frank Yonis, 39, said: “It’s deeply worrying that two bolts can fall off it like that.

“If there had been someone under them when they fell they would certainly have died.”

In 2005 a large window fell out of the 28th floor of the Gherkin building in the City, but nobody was injured.